Diagnostic ultrasound ( PDFDrive )

CHAPTER 28 Overview of Obstetric Imaging 1029
A
B
C
D
FIG. 28.15 Views of Umbilical Cord. Required views include cord insertion site into the anterior abdominal wall (see Fig. 28.12A) and documentation
of number of vessels in the umbilical cord. Additional views include cord insertion site into the placenta and Doppler examination of the
cord. (A) Transverse image of three-vessel umbilical cord. Note two arteries (arrows) that are smaller than the single vein (arrowhead). See also
Video 28.9 and Fig. 28.12D. (B) Color Doppler longitudinal image of three-vessel cord. (C) Cord insertion site (arrow) into the placenta. (D) Spectral
Doppler image documents normal umbilical arterial systolic-to-diastolic ratio in third-trimester fetus.
macrosomia if appropriate. It is important to recognize that if
a pregnancy is redated ater the irst trimester, follow-up is needed
to assess for appropriate interval growth (see Chapter 42).
Identiication of Twin/Multiple Pregnancies
A major beneit of routine ultrasound screening is early
identiication of multiple gestations. 3,16,20-22 Randomized
clinical trials comparing routine second-trimester ultrasound
examination with sonography performed for clinical
indications have shown that a substantial number of twin
pregnancies are not recognized until the third trimester or
delivery in women who do not undergo routine ultrasound.
he improved diagnosis of twins leads to improved perinatal
outcome because of a reduced incidence of low birth weight,
smallness for gestational age, prematurity, low Apgar scores, and
stillbirths. 20
Screening and Perinatal Outcomes
he value of a routine second-trimester scan in apparently normal
pregnancies to identify those at high risk for unsuspected problems
is controversial. Many countries perform one, two, or even three
sonograms as part of routine obstetric care. 21,23,24